Ross MacPhee to discuss ice age extinctions at March 8 Darwin Lecture Series

By Rosie HaneyMarch 2, 2012

Etched in the caves of Rouffignac, France, are images of mammoths, bison and woolly rhinoceros. The drawings, which date back 13,000 years, are some of the only remaining vestiges of an era bygone.

The depicted mammoths, along with about 250 other species worldwide, have gone with the thaw of the last ice age. The event preferentially eradicated “megafauna,” or animals of large body size, such as mammoths and mastodons. But what led to their end? Scientists have suggested several different possibilities, but according to researcher Ross MacPhee, curator of mammalogy at the American Museum of Natural History in New York, the trigger is still missing.

MacPhee will discuss possible causes for the extinction in “Fireballs from Heaven, Climate Change, Emerging Disease, or Men with Spears: Explaining (or Not) Ice Age Extinctions,” as part of the Darwin Lecture series presented by the Ohio Center for Ecology and Evolutionary Studies. The talk will be held at 4 p.m., Thursday, March 8 in the Baker Center Theater.

Ross MacPhee (provided photo).

MacPhee has studied similar losses all over the world, including Siberia, arctic North America, West Indies, Mediterranean islands and Madagascar, to try to pinpoint the cause for Earth’s last major extinction of mammals.

His work, which uses novel approaches such as sampling ancient DNA, has raised many questions about the genetic diversity of extinct mammals and how long it took for them to disappear.

The challenge of studying an event that happened so long ago, however, is finding the right kind of evidence. He parallels the megafaunal extinction with the loss of the dinosaurs around 65 million years ago. While the causes of the ice age extinctions only can be hypothesized, there’s a tangible crater where the meteor struck Earth and prompted the dinosaur extinction. Among other arguments, scientists have suggested that the impact created enough dust to inhibit photosynthesis, which led to the mass death of plants and animals.

MacPhee and his colleagues have cleverly coined terms for the four most widely regarded theories for the extinction: “overkill,” proposing that humans did it; “overchill,” placing the blame on climate change; “overill,” suggesting disease for the mammoth’s end; and “overgrill,” pinning the demise on celestial impact.

If the root of the last extinction is finally traced, it could explain a great deal about what it takes to wipe out so many species in a comparatively short period of time. Was it one of the four popular theories or a combination? How long does the average extinction take? How is it most likely to happen?

MacPhee is not convinced by any of the more dramatic hypotheses for ice age extinctions, and so his work continues.

“At the end of the day,” he says, “we’re missing something relevant.”

The Ohio Center for Ecology and Evolutionary Studies chose MacPhee for the annual Darwin talk for his ability to discuss a topical scientific issue with the general public, according to event organizers Steve Reilly and Pat O’Connor. In addition to the lecture, MacPhee will participate in smaller talks with students and faculty during his visit to Ohio University, they noted.